Variable Similitude
by Primsong
Summary: John Benton only wanted a cup of tea - but everything just went downhill from there. A late-night runaround in UNIT with the Third Doctor, Benton, Yates, the Brigadier and Jo Grant.
1. Chapter 1

**Variable Similitude **

_(or When a Duck isn't a Duck)_

**1.**

If there was one thing John Benton liked best, it was a nice, uninterrupted cup of tea. Piping hot, maybe with a thin-sliced bit of sponge and jam, perfection after a properly uneventful stroll around the perimeter under the stars.

So why was it so difficult to ever have some? Either someone else had eaten all the sponge, the jam was empty or the tea was cold. Or something happened to interfere with his star-gazing (aside from the seemingly perpetual cloud-cover) and he would end up like he was tonight: looking up at the cheery yellow rectangle of window where he knew the tea was brewing and wishing he were there instead of where he was, which was hiding behind a rubbish tip and hoping whatever it was out there would either understand English and be a reasonable sentient creature, or that it would at least be potentially stopped by bullets.

He inwardly sighed and checked his gun. He could just make out one of the sentries from where he was; the man was inexplicably just standing there, as if for all the world there wasn't anything amiss. Benton wondered what had been done to him - surely he wouldn't be so casual if he'd been blinded or deafened. Considering the way things had been going over the past year or so, he decided it was most likely hypnotism which didn't bode well. Frankly, he'd rather face some sort of alien whatsit.

He shifted his stance, alarmed and frustrated. The movement repeated, a slow, man-sized movement coming right up to the sentry, who remained where he was, staring off across the lot as if daydreaming. Benton knew if he were to shout a warning or even give a warning shot it could go badly; the intruder might turn desperate and violent. And if the sentry_ had_ been hypnotised somehow it would do the man no good, and possibly harm him.

The movement of the intruder could now be seen as a silhouette, moving stealthily forward. It lifted up slightly; a taller man, hopefully alone. A motion near the sentry was followed by a faint metallic _click_, the sound of a gun being checked or readied. There was no more time for wondering, Benton knew he had to do something.

The Sergeant stood, his own firearm aimed and steady. "You there! Stop where you are! Drop your weapon!" The sentry didn't even react, but the other figure did; it turned and the arms came upward, but not in a gesture of surrender. And he knew there was a gun.

Nothing for it then. He grimaced and shot, aiming only to wing his mystery adversary, but the other man was moving faster than he'd expected and he didn't know if his aim was true. There was a small cry of pained surprised and the man fell. Benton was out from behind the tip in a flash, running to disarm him while he was down. He had no idea where he'd hit him, but it obviously hadn't been fatal.

As he came closer, his insides suddenly clenched in a different kind of fear. The figure that lay crumpled on the paving in the dim light was someone he knew, and knew well. He bent, gently, fearfully turning the velvet-clad shoulder upward.

It was the Doctor.


	2. Chapter 2

**2.**

Benton winced as he stood against the wall, watching and at the same time wishing he weren't watching. In fact, he thought, he'd pretty much rather watch _anything_ else over a friend being patched up from his very own bungling. The young night medic and his matronly nurse worked to treat the wound that stained the unconscious Time Lord's chest, the nurse consulting the slim file they had on their unusual patient for hints of what they should or shouldn't do and the medic muttering under his breath.

"Don't we have_ any _painkillers he can use?" the medic grumbled. He poked around in the kit he'd set up beside the bed. "Maybe we could try…"

The nurse was shaking her head in consternation. "The directives say not to give him _anything _that he hasn't already approved ahead of time. I wouldn't risk it and if you've any sense you won't either."

"I know, I know, I just hate leaving a patient with nothing. Not even a shot of whiskey seems a bit barbaric."

"He's still out," she noted firmly. "If you move quick, you might get it done before he even wakes up."

"Right, right. That's another thing, why's he out? A chest wound shouldn't knock him out like this, he hasn't lost that much blood and there's no evidence of concussion…besides, some of these notes don't match up with this."

Benton looked away again, feeling simply horrible inside. What had he done? Even moreso though, what had the Doctor been doing? He stepped out of the little room to lean against the wall in the hallway instead. One of the fluorescent lighting tubes was buzzing, which right then was a welcome distraction from the medical discussion.

He pondered the options. He'd seen him creeping up on the motionless sentry, that much was certain. The rest was conjecture. He'd shot him because, well, he thought he was an intruder and about to shoot down the sentry at that. There'd been a gun, that was true, though it was the sentry's own firearm inexplicably in the Doctor's hand. The sentry, who had suddenly snapped out of his strange trance to express nothing but confusion had been no help at all; he didn't remember any of it.

So, Benton thought, if he _wasn't _stealing the sentry's firearm (and why would the Doctor need to be out in the dark hypnotising a man and pinching his gun anyway?) then there had to be another explanation. Had he been out, perhaps checking on that car of his, and been_ returning_ a weapon that had been accidentally dropped? While Benton was inclined to be generous towards the Doctor's pacifist tendencies, this only fit if the sentry had fallen asleep on his feet while holding it and let it slip from his fingers. Extremely unlikely and it didn't explain the man's odd behaviour either.

And now he was unconscious, though he shouldn't be. Benton wondered if he'd put himself under since he was hurt. He sighed. There'd probably be some answer once the Doctor woke up and no doubt it would make sense. He bloody well hoped so.

Either way, he owed him an apology at the very least.

Which reminded him of another person he would have to apologize to: the Doctor's assistant.

If Jo had to hear that he'd shot her mentor, he really would rather she heard it straight from him, not secondhand. And the way word sometimes got about this supposedly secret place, the sooner the better. Tonight, in fact. Before he could lose his resolve, he went to the nearest phone where it hung on the wall, picked up the receiver and doggedly dialed her number.

--

Phones ringing always sounded louder in the dark.

Josephine Grant clicked on her lamp and shook off her sleep, reaching for the phone. Anytime it rang this late at night she always found her heart jumped a bit; she sincerely hoped it was only a wrong number or something. Her aunt had called only this past week to ramble about her uncle's possible heart condition and she'd offered the usual platitudes and comforts to assure it was probably nothing. What if had turned out to be serious after all? The receiver's plastic felt cold against her cheek.

"Hello?"

--

Benton hung up the phone, unsure if he were frustrated or relieved that her line was still engaged. He went back to the little room where the medical night staff were speaking more quietly to one another as they finished up what they could do for now and tried to make their still-unconscious patient as comfortable as possible.

Going out, the nurse nudged the Sergeant with them and gently pulled the door nearly to. "We've done all we can for now. It wasn't as bad as we feared and it helped that he's still dead to the world." She put a hand to her mouth. "Oh, I mean, he's still unconscious, terribly sorry."

The medic gave her an annoyed look and looked up at the Sergeant. "He should wake up soon, and then I'm sure he'll be able to tell us what he needs. Will you be here for a while?"

"Yes," Benton said. "If you need to go wash up, I'll watch."

"Thanks, but the nurse will be right in the next room, so you don't really need to. In fact, I would think if you were his assailant, it might be better to not be right there, if you catch my meaning." The young doctor looked distinctly uncomfortable. "Even if it _was _accidental…sometimes the other chap isn't so understanding at first, and well, there'll have to be a report written up anyway, of course." The Sergeant realised the man was looking at him with something like sympathy.

"Of course," Benton acknowledged with an unhappy nod. "Right. I guess I'll… go take care of the report then."

The medic nodded. "That would probably be best."

--


	3. Chapter 3

**3.**

Jo ran a brush over her hair and grabbed up her purse, trying not to think about the hour. Not that it really mattered, she thought, she so often ended up with late hours with the Doctor. If it wasn't one thing it was another.

She went out, locking the door behind her and clattered down the darkened front steps, sending the neighbor's cat bounding off into the bushes.

--

Sergeant Benton finally gave in with resignation and started down the hall, glancing back at a sound, but it was only the young medic again, coming out of the Doctor's room. He didn't know if the Brigadier was still in the building though he'd indicated he would be working late; he rather hoped he wasn't.

He could imagine exactly the look he'd get from his C.O. and it wasn't a pleasant one. Rubbing at his forehead, he started up the steps, unaware that the medic, still standing by the doorway, was staring fixedly after him.

--

Something made a soft sound nearby in the quiet of the night. The Doctor looked up curiously to see a small green light blinking on and off.

He set aside the tools he'd been working with and went over to his TARDIS, kneeling to examine one of the constructs he'd attached to the various multicolored cables extending out the door. "What's this, old girl? Hm." He poked briefly at what appeared to be a series of plastic squares with lights on them and disconnected the one with the lit-up signal.

"Good work, something going on out there. I'll have to take a look at that later on. Who knows, could be someone interesting to talk to at least, hey?" He patted the blue box companionably then, humming a tune, pocketed the square for later decoding and went back to his tinkering.

--

"So glad you could come, Miss Grant. Again, I apologize for the late hour."

Jo smiled a greeting and slipped her purse from her shoulders, taking the proffered chair. "Or early," she said. "At least I got some sleep, something you look like you could do with. Now. Where's those papers?"

Brigadier Lethbridge-Stewart rubbed at an eye and fished through a pile of folders on his desk. "Early again already, is it? Ah, here we go. The devil take those demmed bureaucrats and their deadlines. If you can just sign here, here and here, we can get these reports off with the earliest couriers."

She leaned forward, reached for a pen and started signing. "I can't even read the Doctor's signature."

He snorted. "Better than some I've seen, and the odds are they won't even care. I tell you, if I weren't an honest working man, I'd just be forging everyone's names on this base. Oh, and here's one more."

--

In the halls below, a young medic moved slowly along, holding his wounded side.

He paused, glancing carefully around a corner, then turned towards the nearby laboratory, his lab coat strangely shifting colours beneath the flickering fluorescent lights.


	4. Chapter 4

**4.**

Jo flourished her name across the line and tapped the papers together. "There you are! Ready to go."

He nodded. "My thanks for your patience with our bungling. You're off home?"

"I might pop in on the Doctor."

"Don't let him set you to working. You're off duty!" he reminded as he held open the door for her.

"Oh, don't worry about me. If I stay, it'll only be because I want to. Or because he looks helpless." She smiled at the Brigadier's half-formed protest and gave a little wave as he closed the office door. She paused partway down the hall to duck briefly into the loo. If the Doctor _did _manage to keep her, it could be a while until she had another chance at it.

A little further down the hall, the tall Sergeant reached the top of the stairwell and paused to square his shoulders and check his uniform before stalking reluctantly down to the Brigadier's door.

Benton barely scraped the wood with his knuckles before getting a response. It looked like the Brig was in after all.

--

The Doctor wasn't entirely surprised to see the Brigadier enter the lab. Alistair seemed to often drift his direction when he was trying to avoid paperwork, at least when there weren't other people around to keep him on task such as in the middle of the night. He usually didn't stay long.

"Good evening, Brigadier," he said amiably, barely glancing up from where he was carefully twisting wires together in his hands. He paused to snip off a rough end with the wire-strippers and looked up again, as there'd been no response. "Anything I can do for you?"

The Brigadier was looking at his TARDIS with more interest than he normally gave the blue box and looked back at the Doctor almost nervously, holding his side. "Can't say its been the best of evenings," he said. "One of my own men accidentally let off a firearm."

The Doctor frowned at this. These military men were always gun-happy, in his estimation, but not generally careless. He tipped his head towards the Brigadier's side. "He didn't hit _you_, did he?"

Lethbridge-Stewart slowly wandered over towards the police-box in the corner, looking down at the tangle of cables that lay across the floor. "Yes," he said briefly. "Been patched up, though. Not to worry."

"The devil!" the Doctor sympathized. "New recruit?"

"No." The Brigadier said, "Sergeant Benton."

"_Benton?_" the Doctor was honestly startled. "He _shot _you? That's rather uncharacteristic of him, isn't it?"

"Demmed bad luck, that's all," shrugged the other. "I've had worse I dare say. What's this do?"

The Doctor frowned again, wondering at his unusual interest. "I doubt you'd understand."

"Try me."

"All right. In essence they're a bit like a radio, you could say. Each one's tuned to a different frequency, though it isn't radio waves they're picking up, but recognizable anomalies. When they detect what they're tuned into they record that information, which I can then review. Does that answer your question?"

"Hm," the Brigadier said. "The little black squares, they can detect and identify aliens then?"

The Doctor gave him a sharp look. "Sort of."

"I see. Hm. Detachable?"


	5. Chapter 5

**5.**

Jo clattered down the steps in her high-heeled boots and seeing the lab door partly ajar, swung around the doorpost to bounce into the room.

"Hello, Doctor!" she said cheerily then suddenly startled at the sight of the Brigadier. "Oh, I'm… sorry, sir. I didn't realize you were here. Couriers already come?"

"What? Oh, er, yes," the Brigadier said vaguely.

"Hello Jo, kind of early for you to be in, isn't it? The Brigadier here was just telling me about his unfortunate mishap with Benton."

"Mishap?" Jo said, plainly confused. "I'm sorry, I guess I missed that one."

"Why, his being shot," the Doctor said, his eyes narrowing slightly.

"Shot?" Jo frowned. "When was this?"

"I didn't want to worry you, Jo," the Brigadier said stiffly. "It's all taken care of. Now, Doctor, about these cables…does each one have a different frequency, then?"

Jo and the Doctor exchanged a brief look. It wasn't like the Brigadier to use her first name so casually, nor to be expressing such interest in the Doctor's constructs and experiments. Something wasn't adding up. He slipped his hands into his pockets casually. "Ah, the cables. Yes, well, they're a bit complicated. Pardon me for just a moment, will you? Jo, sorry to ask you to play hostess at this hour, but could you keep the Brigadier company? You don't mind do you, of course not. Your question just reminded me I had a loose connection that needed tightening down. I'll be right back." He smiled apologetically and slipped past the Brigadier, stepping into the TARDIS.

---

The Brigadier blinked at his unhappy Sergeant, momentarily speechless. "You shot the _Doctor_?"

"Yessir," he said, keeping his gaze fixed on a map against the wall rather than meeting his superior's eyes. "He's still unconscious, but the medics don't know why. I was only trying to wing him, sir. I mean, not_ him_, the intruder. Except it was him."

Lethbridge-Stewart took a breath. "What about the sentry?"

"Snapped out of it but said he didn't remember a thing. Like he'd been asleep, except I don't think he was. I think he was hypnotised, sir. I had him rotate off-duty and schedule a psychiatric evaluation just in case."

"Why would the Doctor be out in the dark hypnotising our sentries?"

Benton's honest eyes finally met his. "I don't know sir. But I'm sure he'll have an explanation when he wakes up."

The Brigadier rubbed his chin. "Yes, I'm sure he will. Endlessly. Plus an extended lecture on the mis-use of firearms as well." He sighed and opened a drawer to pull out a some papers. "There's obviously no reason to hold you in confinement, but I'll need you to sign this form as soon as I write it up. And I'm sorry, but I'll need to confiscate your pistol."

"I understand, sir," Benton said miserably, handing it over.

---

Jo leaned back against the Doctor's workbench and watched as the Brigadier pressed a hand to his side then knelt, picking up the connected stack of little black squares and examining the cable connectors.

"The Doctor doesn't usually like people touching his equipment," she commented. "Sir."

"I'm the commanding officer," the Brigadier said. "And I'll do as I like." He popped one of the little squares off of the rest.

"No, I don't think so," Jo said, reaching over to lock the lab door. "Doctor!"

The Brigadier turned and leapt at her more quickly than she thought possible, snarling, the little clump of squares falling back to the floor. He grabbed Jo and clamped a hand firmly over her mouth, though she bit him for all she was worth. Wrestling the smaller woman sideways, he stuffed her bodily into one of the metal lockers that lined the wall, and after a couple tries, slammed it shut. She beat on the metal.

_"Doctor! Doctor!"_

The Brigadier painfully ran, stooped, back to the cables where he snatched up the loosened black square and stuffed it in his pocket then turned back to unlatch the lab door, his uniform and very shape seeming to waver and flicker as he did so.


	6. Chapter 6

**6.**

Mike Yates hated these extra-early morning hours before the sun had even come up. Night should be night, day should be day. It was only decent. Still, pulling a 'morning' shift that started before it was even morning sometimes couldn't be avoided. The cup of tea he'd swigged before going out the door of his flat had already worn off and he hoped at least have a chance for seconds before having to face any problems.

Making his way through the quiet halls to the canteen he was more than a little surprised to see Jo looking around the room as if completely lost. "Miss Grant? Good morning, if you can call it that," he greeted her, then grew concerned as she startled and turned fearfully towards him. She didn't look well at all. "Are you all right?" he asked, reaching out to touch her shoulder.

Her demeanor immediately changed and she looked up at him with something more like her usual self, reaching up a finger to trace where his name was on his uniform jacket. "Yates! Oh, I'm sorry. I've just had the most awful night, and I'm just …Do you think you might help me?"

"Of course!" Yates said, "What can I do? Do you need to sit down?" Offering a supportive hand to her arm, he reached out a foot to hook a chair from a nearby table. "Really, you look like you could use a medic."

She pressed a hand to her side, shaking her head at the chair. "I already have. I just want to go home."

"Then I'll walk you to the car park," he decided as helpfully he steered her out the door. "Whatever happened?"

She gave a little sob. "Sergeant Benton _shot_ me."

--

Benton signed the papers with resignation. This would be on his record now, he know. Even if it was an accident. He was grateful for an understanding superior officer, but it didn't help his conscience. "I wonder if I might at least check in, back downstairs," he said. "To see if he's awake yet."

"Oh good heavens," the Brigadier suddenly said. "Miss Grant! She was going to check in on the Doctor. She won't have any idea what's going on."

"She's here?" Benton said with surprise. "Well, we can't leave her alone, sir, not with him like that."

"I completely agree," he nodded. "Come on, Sergeant."

--

Mike nodded at the guard on duty at the door and pushed it open, allowing Jo to pass him. She was still holding her side, and he was struggling with concern and consternation over her being hurt in the first place, much less having to hear his own trusted colleague had been to blame.

The car park lay ahead of them, dark and cool, dotted with pools of light that shone off of the few night-crew's vehicles. She hesitated blankly. "I don't see my car," she said after a moment.

"There it is, right down there," he said helpfully, concerned that she might be about to black out if she was missing something so obvious.

"Of course. Thank you," she said and began moving the indicated direction.

"Are you sure you're all right? I could drive you."

She paused, looking back at him, then gave a grateful smile. "Yes, I'm afraid this is taking a bit out of me. Thank you."

Mike nodded and offered his arm again, surprised she'd accepted his help so tamely. His concern went up another notch. "All right, no problem at all. This way."


	7. Chapter 7

**7.**

Having found the small sick-room empty and the nurse completely at a loss to explain it, the two uniformed men came into the Doctor's lab so hastily they bumped shoulders getting through the door.

The Doctor was there, but he gave no welcoming greeting. Alistair abruptly stopped, Benton almost colliding with him as he rocked back on his heels. Their advisor was looking not only awake, hale and whole, he was looking at them with narrowed eyes, coming to his feet with one arm protectively around Jo's shoulders, and pointing a small blinking device in their direction with the other.

"What…" the Brigadier started to say just as the device gave a small chime.

The Doctor immediately relaxed, stuffing it back into his pocket. "It's them, Jo. The real ones, I mean."

She responded to this with relief, jumping forward to take the Brigadier's hand and to give Benton a brief one-armed embrace as they both tried to express their confusion. "I'm so glad! Have you caught him yet?"

"Caught him? Caught who?" asked the Brigadier.

"Why, that look-alike thing, the one that was looking like you!"

"What?"

"We've a very serious incursion here on UNIT property, Brigadier," interrupted the Doctor. "And we don't know yet if it's operating alone or if it has help."

"But she said…" started Benton.

"An incursion?" demanded the Brigadier. "When?"

"Yes, it looked like _you_ and it managed to fool us for a few moments. I stepped into the TARDIS to run back the readings I'd gotten earlier on something in the area - to find out what we were dealing with - but it attacked Miss Grant and ran off before I could finish. I think it's wounded."

"_Good _job, Miss Grant," said the Brigadier.

"Oh no,_ I _didn't hurt it," said Jo. "Except maybe its hand. I did bite, I admit. It was already acting hurt."

Benton's brow furrowed. "On its side?"

"Yes," the Doctor said. "And what's more, it made up some ridiculous story about _you _shooting it."

They all looked at Benton. He was suddenly smiling. "So it _was_ an alien intruder! I can't tell you how glad I am to hear that I didn't shoot _you,_ Doctor. Really!"

"Shoot me?" the Doctor said.

"It looked like you when I first saw it," he explained. "So after I shot it, we had it brought inside, of course."

"You shot the _Doctor_?" Jo said in disbelief. "I mean, even if it wasn't…"

"I didn't see the resemblance until I was right up to it," he said, embarrassed.

"Yes, well, we'll iron all that out later," the Brigadier announced. "Doctor! What do can we do to catch this thing, and is it armed?"

"I don't think so. The piece it stole from my lab could be used for communication, but not as a weapon. It's weapon is a talent for apparent similitude."

"A what?"

"Camouflage. It could appear as any one of us and I expect it's probably trying to get back off the property."

"Looked like me, did it?" the Brigadier mused. "How does it know who to look like?"

"Most likely using a minor psychic connection," the Doctor brushed it off. "Picking it up from other people's minds in the nearby area."

"I don't like that," Jo noted uncomfortably.

"Oh, it doesn't hurt."

"That's not what I meant."

Lethbridge-Stewart tapped his heels together. "You know what it is, then?"

The Doctor made an impatient gesture. "Any one of a half-dozen races, I've narrowed it to four. This," and he drew the small object back out of his pocket, "is set to a frequency that tests for variable shape-shifting abilities."

"An alien-detector," the Brigadier said with satisfaction. "What are we waiting for then?" Ignoring the Doctor's annoyance at this over-simplification, he turned to the lab phone and punched in a number. "This is Brigadier Lethbridge-Stewart. No one is to leave this property until further orders. That's right, not even myself. No one. We have an alien incursion. I want all the exits sealed, interior and exterior. The Doctor is helping us track it down. Yes, that's right. All."

--

"Sorry, no passage," the gate-keeper said sternly.

"I'll be coming right back," Yates said. "You need this?" He unfolded his ID and held it up.

"Sorry sir, I meant no one is to leave the premises. Brigadier's orders."

"But this is Miss Grant. You know her. She's been hurt, and she needs to go home!"

"Sorry, sir. Orders are orders. I'm sorry she isn't feeling well, but there's a medic inside if she needs it."

"But…" Yates started, then stopped and blew out his cheeks with annoyance. The gate-keepers expressions were firm and one of them reached for a rifle.

Irritated, Mike set the car into reverse and backed it into an empty parking space. He turned to Jo. "I'm sorry you had to be caught up in this. It probably won't be too long; I mean, last time we had this happen it turned out to be a stray dog. You know how it is."

"But what if it really _is_ an alien this time?" she said. "The Sergeant wasn't acting himself at all. What if it wasn't really him?" She hugged herself and winced. "What if he tries to shoot me again?"

"He won't hurt you again, not as long as I'm here," Mike assured her.

She didn't seem to be listening to him. "I don't want to be caught sitting here in a car," she said suddenly and opened her door, causing Yates to scramble out his own side and come around to help her out. She began nervously walking along the perimeter of the wall, so after a moment's hesitation he walked with her.

--


	8. Chapter 8

**8.**

"All right," said the Brigadier. "Benton, you come with me. We'll come around this way, you and Miss Grant go the other."

"Wait!" Jo said. "If we see it, we'll need some way to tell it apart from the real Brigadier."

"I have this," the Doctor said, gesturing with his blinking device.

"You do, but the rest of us don't," she insisted. "I know! Take off your coat!" She reached out and to his surprise began tugging at the collar of his burgundy velvet jacket. "The Brigadier can wear it."

"What?" the Brigadier and the Doctor protested together. Nevertheless, he allowed her to take it, and Lethbridge-Stewart allowed it to be foisted off on him. Jo could be very persuasive.

"There. That's better. If it still looks like the Brigadier everyone thinks of in their heads, we'll know it's a fake. No one would be imagining him in velvet," Jo said reasonably.

The Brigadier looked down at his non-lacy cuffs poking out from the velvet. "Not my style," he commented.

"I'll have to agree with that," the Doctor grumbled as he smoothed his waistcoat. "But she has a point. Now, let's go."

--

Benton carefully worked his way along the outer perimeter, half an eye on where the Brigadier was working along the inner so he didn't outpace him. He slowed as the Brig began systematically going through the long line of trimmed boxwood shrubbery that had been grown along the side of the main building. They were nearly done with this side; the car park would be next and he didn't look forward to that one. Walking slowly forward, he kept scanning all around. Up ahead two figures rounded the corner walking along the wall, one shorter and one taller.

"Hey! You there, stop right there. Hands in the air," he ordered firmly.

The figures stopped at the edge of one of the pools of light, then one of them gave a little cry of fright, hiding behind the other. "It's him! Don't let him get me, Mike!"

Benton gaped a moment. Jo? But he'd just left her, going the other way around the building with the Doctor. Across from him he could just see the Brigadier in the boxwoods, quietly reaching for the pistol he had beneath his incongruous jacket.

"Leave her alone!" Yates challenged, keeping the girl behind him. "Haven't you done enough damage already? What's wrong with you?"

"Captain!" Benton warned, "It isn't what it looks like. You! Step away from him, hands where I can see them!"

The girl began to cry, something that unnerved them both as it was something she rarely did.

Both confused and angered, Yates stepped forward. What if Miss Grant was right and something had gotten ahold of his fellows, or worse, was mimicking them? "No, _you _get _your_ hands up,_ Sergeant_, if that's who you _really_ are."

"All right, that's enough!" the Brigadier said, stepping out from the bushes. He had his pistol out.

Yates gaped at his superior officer clad in red velvet. Something was_ obviously_ wrong here.

There was a clatter of heels on the pavement. She was running away into the darkness. Yates still stood, surprised at her retreat but covering for her, arms spread out. "Leave her alone," he repeated. "What do you want?"

"For you to get the hell out of the way," the Brigadier growled as he ran after the girl, Benton following.

Yates reached belatedly for his own sidearm, only to remember he didn't have it with him. The Brigadier was already barreling past him, so he did what he could: he tackled Benton. "Run Jo!" he cried as the two men fell painfully to the pavement together.

"Oof! It's not Jo, it's an alien!" Benton snapped. "Let go!"

Yates hung on. "How do I know it isn't _you _that's the alien? You _shot her!_"

"I did_ not!_" Benton protested, trying again to regain his feet. "She looked like the _Doctor_ when I shot her!"

"What…." Yates was suddenly cut short by a firm hand grabbing his shoulder and spinning him off of the Sergeant.

The Brigadier's eyes shot daggers at his unfortunate Captain. "Now you've done it; it's gotten away. Come on, both of you. I don't care what your opinions are on it, Captain, but I expect you to listen. Benton, continue around the wall. Yates, with me. It's somewhere between us and the Doctor and I've just had the entrances to the buildings sealed off. We'll find that blasted thing yet."

"But Miss Grant…" Yates started, still feeling like the entire world had taken a surreal twist. He automatically followed his officer.

"Wasn't Miss Grant," the Brigadier finished tersely. "That creature can look like _anyone,_ apparently. Watch for anyone who's been wounded."


	9. Chapter 9

**9.**

Like the other pair, the Doctor and Jo had spread apart, her covering the area nearest the building while he scanned over the assorted small sheds, boxes and piles of whatnot that were along the back wall.

They met one sentry near the munitions storage, who gave a greeting but hadn't seen anything unusual, then moved on around the corner towards the mechanics' sheds. There was nothing moving to be seen, only a small aircraft that droned overhead on its way to the airport. Nearing the end of the stretch, Jo signalled all clear from her half and the Doctor responded in like. Up ahead they could just make out the other night sentry, who seemed to be looking the other way.

He gestured to her and together they slipped into the sheds, though he briefly extended an arm back out and pointed his 'alien detecting' device towards the sentry. Nothing.

"He doesn't look like he's hurt anyway," Jo whispered.

"True." He went deeper into the mechanic's shed, holding the tiny yellow light out in front of him like an ineffective torch. After a pause to listen, he began to quietly work his way around the back of the assorted vehicles.

She tip-toed after him. "You know, I never thought I'd say it, but I'm really glad Benton shot you. It makes finding this thing easier."

"You could have put that differently."

They finished the main bay and slipped through the door that separated it from the smaller one. This one they knew well as it included Bessie. The Doctor held up a hand and Jo froze. The light had changed to green. He panned around, then indicated the back wall of the building. It had to be on the other side.

Jo gave an inquisitive look and walked her fingers in the air to indicate their going around. The Doctor considered it, then shook his head and mimed something else.

---

"If you weren't such a good officer, I'd boot you out for being a damn fool," the Brigadier grumbled to Yates as they walked. "At least Benton had the good sense to shoot the blasted thing, even if it did look like the Doctor. Not that there aren't times I haven't wanted to shoot him myself…" he paused to peer more closely at a person-sized lump, but it was only a gas meter. Yates, feeling thoroughly chagrined and humiliated, had already known it was the meter, but had the good sense not to point this out..

"Pull up your shirt," Benton ordered the sentry he'd encountered. The man gave him a strange look, but in the face of the Sergeant's no-nonsense tone, he obediently pulled his jacket aside, untucking his shirt. The Sergeant prodded his ribs suspiciously, then let him go.

"You're to stop _anyone_ who seems even remotely wounded. Anyone, I don't care if it's the Brigadier, the milk-man or the Queen. You understand? Good man." He stalked off into the darkness, leaving the baffled sentry behind.

They finished the car park and the side of the main building. The Brigadier signalled to Benton, who came over to join them. "We should've met up with the Doctor by now," he noted. "Could be something's gone wrong. Be on the alert."

"Yes sir," Benton agreed. "Do you think that thing could've turned into something that climbs walls?"

Yates shook his head. "If it could climb walls or just fly off, wouldn't it have done that in the first place?"

There was a burst of noise around the corner. They all immediately ran, automatically checking their fire-arms, though only the Brigadier had one.

"Ah!" he said as they rounded the corner. "Well done."

\


	10. Chapter 10

**10.**

Inside the darkened shed, there suddenly came a huge metallic bang on the wall and an excited shout. "We've got it now! It can't escape!"

The sentry spun around, putting his gun at ready as out from behind that same building there was a sound of rapid heels on the pavement and a young woman came staggering out of the darkness, holding her side as if in pain.

The sentry had been alerted that something was amiss so no one was to leave, but he lacked any other detail. He was astonished. "Miss Grant?" All the men knew the Doctor's pretty assistant, if only in admiring her from afar. What was she doing out here at this hour, and alone, and what was that sound?

"Help me! You've got to help me!" she said, one hand grabbing onto his arm with more strength than he would have thought possible, the other pressed to her chest. "They've all gone mad! I don't know why, it's like some kind of alien's taken them over!"

"What?" He'd heard of the lock-down on the premises, but had no idea it was this bad.

"Please help me, they're serious! I've already been shot, the medic managed to help me, thank goodness, before they all came after me again. The Doctor and the Brigadier, and the Captain…"

The sentry's eyes grew round at this, then his jaw hardened grimly. "Shot? Stay with me, Miss. They won't hurt you again. We'll see what's up." Still holding his gun at ready, he scanned the darkness around them. "Do you have any idea who it was that shot you? Was it an alien?"

"No, it was Sergeant Benton," the girl said, then after a moment followed this announcement up with a small sob.

_"Benton?_" the sentry asked, shocked anew. She might as well have said she'd been shot by the Pope, if he hadn't already heard other disturbing news that night. "I heard he'd accidentally shot the Doctor," he said. "Something's very wrong here. John would never…"

"Him too," Jo was nodding beside him belatedly. "Yes, yes, oh the poor Doctor!"

The sentry frowned at her. "Wait. You said the Doctor was one of 'em coming after you. How could he be doing that if he was shot?"

She looked confused, then looked away. "He, he was changed somehow. I don't know, he, he got back up and then told them to grab me! After what happened with Benton, I was scared."

The sentry's brow creased. "All right," he said slowly, his gun lowering slightly. "I don't know what that was, but I don't see anything. I better call the Brigadier."

"He's one of them too!" she said and hid her face in her hands.

His frown deepened. Now he thought he could hear movement in the yard nearby. What if it was the Brigadier? What then? An alien incursion that had taken over all of the commanding officers _and _the Doctor would have to have been formidable. A shadow moved near the edge of the mechanic's shed and he adjusted his stance.

"Who goes there?" he challenged, trying to see inside. "Put down your weapons! Come out with your hands up!"

"Don't let them catch me," the girl was saying behind him. She sounded further away. He risked a glance back to see she was slipping back, backpedaling away from his position and eyeing the nearby wall.

A car suddenly roared to life and plunged out of the shed, its lamps flaring up, ablaze. Gasping, the sentry jumped out of the way as it shot past, tyres spinning for traction. He whirled, turning to see, to his horror, it was the Doctor's car - _and it was bearing down on Miss Grant! _

The girl was running, faster than seemed humanly possible, running for the wall that enclosed the compound. Helplessly he watched, sure she was going to be run down, fumbling for his weapon he belatedly let off a shot at the back of the car, hoping to hit a tyre, to no effect.

And Jo, caught in the twin beams, suddenly turned, uncharacteristically snarling as she jumped for the wall. The car squealed to a stop, a tall figure careening out and running to intercept her, tackling her smaller frame in a great flying leap to bring them both tumbling down among the weeds and gravel.

"Oh, nicely done!" crowed the second person, jumping from the car with ready handcuffs flashing in the lights.

"Eh?" the sentry blinked in astonishment. It was Miss Grant…again. Something wasn't right.

"Well done," came a familiar voice behind him. He turned to find the Brigadier himself jogging up to the scene. He was dressed in velvet. Behind him came Captain Yates and further behind, Sergeant Benton. Confused and intimidated, he fell back to standing at military attention with eyes straight ahead and hoped the madness would all just pass him by.


	11. Chapter 11

**11.**

The Doctor smoothed his coat, finding yet another bit of boxwood caught in the pocket. He flicked it away and pulled out a black square, turning his attention back to the beige-dressed somewhat balding man that waited in the middle of his lab.

The Brigadier came in the room just as the phone rang. He reached out an arm and snagged it. "Lethbridge-Stewart… Look I don't care if it's the Prince of Wales you see in that room, you aren't to let them out! Right." He banged the receiver back down and pivoted to greet their visitor.

"Brigadier Lethbridge-Stewart," the Doctor introduced with a nod between them. "Parole Officer Statz. The Brigadier is the one you need to be thanking, he's in charge of this facility and it was his man that detected your renegade."

The beige man's head bobbed towards him. "As I was telling your Doctor here, we greatly apologize for the inconvenience."

"What was that chap doing here in the first place is what I want to know," said the Brigadier. "And are there more of your kind about?"

Statz opened and shut his mouth like a fish, as if he weren't sure how to respond. The Doctor interrupted. "It appears Earth was chosen as a minimum security prison, if you will, but only recently. They understand now that is it _not _an acceptable dumping ground for criminals, no matter how seemingly harmless."

"I should expect so," snapped the Brigadier, his face impassive. "Now if you'll be so kind…"

"Of course, of course." He followed the Brigadier, who, along with Captain Yates, was overseeing the transference of their prisoner back into the hands of its own kind.

"Really, there was no need to be rude," the Doctor said when he returned. He was busy carefully aligning his little black squares again. "They're not all bad; near as I could tell, our troublemaking mimic was merely left here for gambling debts. I'd like to have learned more about the way they pick up mannerisms as well as the shape of what they're mimicking - though they're only a variety of imperfect polymorph."

"Imperfect," echoed the Brigadier with a snort. "Any tea left?"

"They seem to have a psychic connection to mimic and influence the people around them into accepting them the way they are," the Doctor continued as the Brigadier, finding himself ignored, went to check the level in the pot himself. "It makes up for the imperfection of the copy."

"What did he want here anyway?" The Brigadier upended the pot, gaining only a dribble of tea.

"Oh, he got what he was after." The Doctor held up the black square with its light on it. "Something he could both track his own parole officer with _and_ signal his former cronies that he was ready to bargain again. Near as I can ascertain, he was in the process of stealing the sentry's pistol prior to breaking in. Of course, we ended up carrying him right inside which must have simplified things. No doubt he used that minor psychic influence on that sentry as well, then."

"He thought he'd fallen asleep on his feet, poor chap," Benton noted from where he sat on the lab sofa, gratefully sipping from a small mug. Jo was half-propped up at the other end, a small plate of sponge-and-jam in her limp hand and her head back, sound asleep.

"Oh yes, it seems to have been relatively benign, merely a push into the initial levels of sleep, such as a hypnotist might achieve."

"I thought he seemed hypnotized. In fact, I was afraid it was…you know who."

The Doctor raised his brows at this and rubbed his chin. "Ah. Well, I suppose no one can blame you for that."

"Still sorry I shot you, though. Won't do it again."

"Not if you can help it, hm? Yes, I hope so as well."

--- fin ---


End file.
